According to the characteristics and requirements of weighing process for liquid raw material, the system of data acquisition and control based on serial port communication is designed in this paper. The system adopts the modularizing distributed structure and the way of RS485 communication to ensure the reliable data transmitting between IPC (Industrial Personal Computer) and modules. Based on C++ Builder 6.0 and SQL Server 2000, the system not only implements the process control of weighing and blending, but also realizes the production data storage and management. This paper analyzes the system function structure, describes the method of communication and introduces the means of data management. The application result indicates that this system improves the production efficiency and stabilizes the production process.